Technologies


A Method for Using GPS and Crosslink Signals to Correct Ionospheric Errors in Space Navigation Solutions

Reference#: P01814


Distributed spacecraft systems (e.g. distributed satellite systems or spacecraft systems with some type of propulsion device) use multiple spacecraft to augment the capabilities of monolithic space system approaches. These systems, also referred to as formation flying systems, enable complex sensing tasks such as distributed aperture processing, co-observation, multipoint observation, and distributed interferometry, which are beyond the abilities of single spacecraft systems. Depending on the degree of inherent coordination, formation-flying systems differ from traditional satellite constellations in that the distributed system is treated as a whole, unified by common objectives. Both the National Aeronautics and Space Administration (NASA) and the Department of Defense (DoD) have identified distributed spacecraft systems as a means to achieve mission goals in future deployments. NASA, for example, has identified campaigns of several space missions that largely rely on multiple spacecraft deployments. Operationally, such systems are in their infancy.

A significant number of Earth and space science goals rely on the successful deployment and operation of distributed spacecraft technology within future operational missions. In conjunction with fundamental science, distributed spacecraft military missions in support of defense operations have been identified as important capabilities to maintain national interests.

It is, therefore, an object of the present invention to provide a method for utilizing GPS and crosslink signals in distributed spacecraft systems to correct for ionospheric errors in space navigation solutions, specifically, for relative navigation.

According to a first embodiment of the present invention, the above and other objects are achieved by a method for utilizing GPS and crosslink signals in a distributed spacecraft system having crosslink capabilities to correct for ionospheric errors for relative navigation using pseudorange measurements. The method comprises: obtaining a first GPS measurement set in a first spacecraft of the distributed spacecraft system from a GPS system; obtaining a second GPS measurement set in a second spacecraft of the distributed spacecraft system from the GPS system; computing a first relative range vector between the first and second spacecraft from the first and second GPS measurement sets; determining a second relative range between the first and second spacecraft from a crosslink signal between the first and second spacecraft; estimating a true scaled relative displacement of the first spacecraft with respect to the second spacecraft using a norm of the first relative range vector and the second relative range; and compensating the first relative range vector using a function of the true scaled relative displacement.

In a second embodiment of the present invention, the above and other objects are achieved by a method for utilizing GPS and crosslink signals in a distributed spacecraft system having crosslink capabilities to correct for ionospheric errors for relative navigation using carrier phase measurements. The method comprises: obtaining a first GPS measurement set in a first spacecraft of the distributed spacecraft system from a GPS system; determining a second GPS measurement set in a second spacecraft of the distributed spacecraft system from the GPS system; computing a first integer resolved relative range vector between the first and second spacecraft from the first and second GPS measurement sets; determining a second integer resolved relative range between the first and second spacecraft from an integer resolved crosslink signal between the first and second spacecraft; estimating a true scaled relative displacement of the first spacecraft with respect to the second spacecraft using a norm of the first integer resolved relative range vector and the second integer resolved relative range; and compensating the first integer resolved relative range vector using a function of the true scaled relative displacement.

Patent Status: U.S. patent(s) 6859690 issued.

CONTACT:
Dr. G. R. Jacobovitz
Phone: (443) 778-9899
ott-techmanager3@jhuapl.edu

Additional References:

Link to U.S. Patent and Trademark Office
Patent Drawing